People pass under Kurdish flags in Irbil, 217 miles (350 kilometers) north of Baghdad, Iraq, Saturday, Sept. 23, 2017. Iraq's Kurdish region will vote on Monday's referendum for Kurdish independence, a vote dismissed as illegal and destabilising by the central government and the international community. (AP Photo/Khalid Mohammed)

The referendum is set to be held in the three provinces that make up the Kurdistan region as well as multiple towns and villages that are claimed by the Kurds and the Iraqi central government.

"Already the referendum has negatively affected Defeat-ISIS coordination to dislodge ISIS from its remaining areas of control in Iraq," Nauret added. "The decision to hold the referendum in disputed areas is especially de-stabilizing, raising tensions which ISIS and other extremist groups are now seeking to exploit."

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Baghdad orders Kurdistan region to hand over borders, ports

Khalid Mohammed/AP

Kurdish flags and pro-independence items on display for sale near an open-air cafe in Irbil, 217 miles (350 kilometers) north of Baghdad, Iraq, Saturday, Sept. 23, 2017. Iraq's Kurdish region will vote on Monday's referendum for Kurdish independence, a vote dismissed as illegal and destabilising by the central government and the international community. (AP Photo/Khalid Mohammed)

Khalid Mohammed/AP

Khalid Mohammed/AP

Men buy sunglasses from a street vendor underneath Kurdish flags in Irbil, 217 miles (350 kilometers) north of Baghdad, Iraq, Saturday, Sept. 23, 2017. Iraq's Kurdish region will vote on Monday's referendum for Kurdish independence, a vote dismissed as illegal and destabilising by the central government and the international community. (AP Photo/Khalid Mohammed)

Khalid Mohammed/AP

Khalid Mohammed/AP

The President of Iraq's autonomous Kurdish region, Massoud Barzani, speaks to reporters during a press conference at the Salah al-Din resort, in Irbil, Iraq, Sunday, Sept. 24, 2017. Barzani said Sunday, that the controversial vote on independence will go ahead as planned and that while the vote will be the first step in a long process to negotiate independence, the region’s “partnership” with the Iraqi central government in Baghdad is over. (AP Photo/Khalid Mohammed)

Khalid Mohammed/AP

Khalid Mohammed/AP

People pass under Kurdish flags in Irbil, 217 miles (350 kilometers) north of Baghdad, Iraq, Saturday, Sept. 23, 2017. Iraq's Kurdish region will vote on Monday's referendum for Kurdish independence, a vote dismissed as illegal and destabilising by the central government and the international community. (AP Photo/Khalid Mohammed)

Khalid Mohammed/AP

The Kurdish region's president Masoud Barzani vowed to go ahead with the vote despite pressure from Baghdad and the international community. He said the referendum will be the first step in a long process to negotiating independence.

"Only through independence can we secure a future where we will not have the past atrocities," Barzani said, referring to the killings that occurred at the hands of Saddam Hussein's army that left more than 50,000 Kurds dead.

Late Sunday night, Iraq's central government in Baghdad ordered the Kurds to hand over all border crossings and airports.

Iraqi Prime Minister Haider al-Abadi also re-emphasized his call for the vote to be canceled.

"The map of Iraq is suffering attempts at division and tearing up of a united Iraq. Discrimination between Iraqi citizens on the nationalist and ethnic foundation exposes Iraq to dangers known only by God," al-Abadi said.

Iran, which shares a border with Sulaymaniyah, Kurdistan, closed its airspace to flights taking off from the region ahead of the controversial vote.